Input protection circuits are commonly used to prevent excessive input voltage levels such as electrostatic charges from destroying circuitry coupled to an input terminal. Many varieties of input protection devices exist. Some include a spark gap protection scheme wherein a metal strip which is separated by a gap of predetermined width is coupled between an input terminal and a ground reference. Whenever a large input voltage is coupled to the input, the excess voltage is allowed to conduct across the gap and be diverted to the ground reference and away from the circuitry. A metal plate for this type of protection has restrictive processing limitations and requires more circuit area than is often desired. Other input protection schemes typically utilize a pair of diodes which may shunt positive and negative voltages greater than a predetermined diode barrier breakdown voltage. A disadvantage with this type of input protection is the fact that such circuits typically do not allow larger operating voltages such as twenty-five to thirty volts to be coupled to the circuitry. In many applications, such as the telecom RS-232 standard, such operating voltages are used. Avery, in U.S. Pat. No. 4,400,711, teaches a protection device which permits input voltages exceeding a circuit's power supply voltage to be coupled to the circuit before input protection voltage shunting is utilized. The breakdown voltage which triggers the input protection in the Avery circuit is dependent on the threshold voltage of an MOS field effect transistor and is typically limited to a maximum value of about sixty volts.